Method for operating a membrane filter having a gas discharge cleaning means

Abstract

Operation of a membrane filter includes the step of selectively supplying gas into the compartments of a membrane unit 50 composed of an array of membrane elements 51 disposed within a treatment tank 31 . A skirt element 71 is disposed at a bottom portion of the membrane unit and an aerator 61 is disposed under the skirt. A partition is also disposed at the bottom of the membrane unit forming compartments within the shirt element. The gas bubbles discharged from the aerator increase their rising force upon entry into gaps between the membranes. Because of the arrangement of the partition within the skirt element the flow rate of bubbles along the opposite side edge portions of the membrane unit can be increased having the advantage of cleaning the entire surface of each membrane, thereby preveting clogging by sludge, SS, colloid, etc. within the gaps between the membranes. Therefore, filtration can be maintained over a longer period of time and the power required for filtration can be reduced, as well as, the frequency of manual periodic cleaning, chemical cleaning, etc.

What is claimed is:  
     
       1. A method for operating a membrane filter apparatus comprising a treatment tank; a membrane unit disposed within the treatment tank and composed of an array of membrane elements extending in an arraying direction; a tubular skirt element having a first end disposed at a bottom of the membrane unit and a second end positioned adjacent a bottom of said tank; 
       an aerator disposed under said skirt element and adapted to discharge gas;  
       at least one partition disposed at a bottom portion of said membrane unit along the arraying direction and extending downwardly therefrom a major portion of the distance between said first end and said second end of said skirt element, said at least one partition and said skirt element defining at least two compartments within said skirt element; and  
       gas supply means for supplying gas into the at least two compartments,  
       said method comprising a step of selectively supplying gas into the compartments.